Datsun 240Z Restoration: It Lives!

So nice to have this under my belt. After ordering all the parts on my spreadsheet:

I set about getting the Z’s engine running, even if the car itself isn’t yet mobile. Here’s what was done:

Replaced all engine bay coolant hoses, replaced coolant

Drained, cleaned and re-sealed fuel tank

Flushed all fuel hardlines and replaced all rubber lines

Set valve clearances, replaced valve cover gasket:

Removed intake manifold coolant pipe and plugged passages

Had carbs rebuilt

New battery

Replaced thermostat, oil pressure sensor, fuel pump and filter…

…along with a few other odds and ends. Filled the tank with a few gallons of 93, added 5 fresh quarts of 15W-40 Rotella T heavy duty oil (love the stuff) and a new filter, and on Wednesday evening…cranked it. The results of the first attempt can be found here—while the engine started, it immediately began to cycle between racing and bogging in the exact manner it had before I parked it eight years ago. By juggling the choke and throttle, I managed to stabilize things long enough for the engine to warm up, at which point I was able to use the idle screw to keep it running. But the engine was still missing and sputtering, something obviously wrong.

I was bummed. I didn’t hear any knocking or tapping that would indicate internal damage from the no-oil-pressure incident, but I wondered if somehow the cycling idle might be caused by something I’d done, though I wasn’t sure how it could be connected to a loss of oil pressure without some accompanying metal-on-metal noise.

Still, as another Z owner pointed out, it started, it stayed running, and it didn’t overheat. So there was that. The critical bit of information came from yet another Z owner, Frank in Houston, who right away saw that the outlet pipe on the balance tube for the (removed) air pump was unplugged, creating a huge post-throttle vacuum leak. The behavior of the engine on first startup was so dramatic that I didn’t see how plugging the pipe would make a substantial difference, but…did it ever. The surging idle completely disappeared, replaced by a perfectly-running, docile and tractable still-untuned engine. Amazing. And extraordinarily encouraging.

The upshot is that the engine wasn’t ruined by the no-oil-pressure incident, so I’ll simply pull it and clean it up in lieu of totally rebuilding it, reducing the cost and time of the restoration exponentially.

Now I’ve just got to get it back on the road for a “last hurrah” before I park it for the resto, which means…brakes and clutch time. Onward!

Editor’s note: This post is Part 14 of an ongoing series chronicling my efforts toward the restoration of my 1972 Datsun 240Z, originally my father’s. Read the other installments here:

5 Comments

Oh man. I can feel the pride and satisfaction from all the way over here. That must be wonderful. The car sounds great. Way to go, Matt. You working on that car brings back memories for you and me both, my friend. Carry on. ;)

I just can’t help it – how many times do we harp on about vacuum leaks on the forum!! :P Oh well, at least you found it and fixed it, now you can enjoy finishing all the smaller detail stuff and get it purring properly. Moar vids!!